The purpose of this project is to form a cooperative effort in order to provide a focused evaluation of the capability of improving electron beam dose distributions with presently available beam delivery systems, imaging systems and computerized treatment planning systems. Evaluation of the role of tissue inhomogeneity corrections, error analysis, advanced beam transport calculations and dynamic treatment will also be made. The Principal Investigator and key personnel from each of the three Contracts awarded under this project will form a Working Group. Each Contractor in the Working Group will calculate treatment plans for patients in treatment sites representing major anatomical areas. The specific sites and numbers of patients will be determined by the Working Group. Calculations will be performed using tissue data derived from CT scans and plans will be optimized for technique of delivery, electron energy and correction for tissue heterogeneity. Error analysis and evaluation schemes will be developed to evaluate plans. Calculations will be verified by measurements in patients and phantoms. Recommendations and guidelines will be developed for the application of findings to the practice of radiotherapy.